Optimization of film bulk acoustic wave resonator (FBAR) for RF filter applications

In this paper, we present the effects of the thermal annealing of the W/SiO/sub 2/ multi-layer Bragg reflectors on the resonance characteristics of the ZnO-based film bulk acoustic resonator (FBAR) devices and the use of the cobalt (Co) electrodes instead of the aluminum (Al) electrodes to optimize the FBAR for RF filter applications. The resonance characteristics could be significantly improved by the thermal annealing and using the Co as the electrodes in FBAR devices. The FBAR devices with the Bragg reflectors annealed at 400/spl deg/C/30 min show excellent resonance characteristics in term of the return loss and Q-factor.